Note: Descriptions are shown in the official language in which they were submitted.
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SECURITY ELEMENT FOR DOCUMENT OF VALUE
This invention relates to security elements for documents of value such as
passports, identification cards, banknotes, certificates and the like, methods
of
manufacture thereof and corresponding authentication systems.
In the field of security documents, there is an ever present need to ensure
the
authenticity of the document and deter potential counterfeiters. With this
aim,
documents of value such as passports, identification cards, licences,
banknotes,
certificates and the like are commonly provided with security elements which
are
difficult, if not impossible, to reproduce without sophisticated equipment.
One
category of such security elements is perforated features, such as the
perforated
serial number typically found in passport booklets. Perforated features such
as
these enhance the security of the document since the feature cannot be
reproduced by photocopying or printing, but must be formed in a separate
processing step, thus enhancing the difficulty of making a copy of the
document.
In addition, an existing perforation cannot easily be altered in an
unnoticeable
manner. Whilst perforations can be formed by mechanical means, such as
perforation pins, the security can be still further enhanced by specifying
that the
perforations are to be formed by laser, which not only enables a more
intricate
perforated design, but additionally imparts characteristics such as a
darkening of
the material forming the document, which cannot easily be imitated. Since the
cost of suitable laser perforation equipment is high, this presents a further
barrier
to the potential counterfeiter.
However, due to their very visible nature and relative ease of manufacture
compared to other forms of security element (such as holograms or magnetic
features, for example), perforations alone are generally not considered to
provide a document with adequate security. In addition, the amount of
information which can be carried by a feature such as a perforated serial
number
is limited. A number of approaches have been proposed for enhancing the
security of perforated security elements. For example, in EP-A-0861156,
perforations of very small diameter are arranged to form a pattern which is
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visible in transmitted light but invisible in reflection to the naked eye. US-
A-
2006/0006236 discloses a perforated grid in which elongate holes are arranged
in two orientations such that, when the document is viewed at an acute angle,
a
latent image is revealed, since those apertures aligned with the direction of
viewing will transmit more light than the others.
In WO-A-95/26274, the high level of detail available through the use of a
laser
beam to produce perforations is made use of by applying fine structures such
as
a wave-like edge to an otherwise conventional perforated number in order to
individualise the document. Finally, WO-A-02/39397 discloses the inclusion of
secret codes in a perforated serial number by shifting the perforations along
various axes or changing the point diameter of certain perforations, amongst
other examples.
In accordance with the present invention, a security element is provided for a
document of value, the security element comprising an array of apertures
through at least a portion of the document of value, the arrangement of
apertures relative to one another forming an observable data item, wherein the
array of apertures comprises apertures of at least two different shapes or
orientations, the occurrence of the different shapes or orientations within
the
array representing an encoded data item.
By encoding a second data item within a perforated element through the use of
different aperture shapes or orientations, not only is the information
capacity of
the element greatly increased, but also its security, since the meaning of the
encoded data item (and hence the ability to reproduce it) will not be apparent
to
an observer unless they have knowledge of the manner in which the different
shapes or orientations are selected in order to represent the encoded data
item.
In this way, the difficulty of making counterfeit security elements (e.g. for
a
fraudulent passport) is greatly increased since not only will the
counterfeiter
have to form the correct observable data item (such as a perforated serial
number to match that printed on a data page of a passport booklet) but,
additionally, they must form the observable data item from apertures having
the
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correct assortment of shapes or orientations according to an algorithm or
other
scheme which is unknown to them. In addition, the inherent difficulty of
manufacturing the perforated security element is also increased, since the
counterfeiter will require apparatus capable of producing apertures of the
appropriate shapes, such as multiple perforation pins of different outlines or
precisely controllable laser perforation equipment.
The "shape" of an aperture refers to its geometrical outline. Shapes may
differ
from one another by having a different number or configuration of sides,
different
lengths of the sides relative to one another, a different number, arrangement
or
angles of corners, or at least a different aspect ratio. For instance, two
circular
apertures, one having a larger diameter than the other, would not be
considered
to be of different shapes since the essential outline of each is the same,
differing
only in scale. In contrast, a first rectangle having long edges twice as long
as its
short edges would be considered a different shape from a second rectangle
having long edges three times as long as its short edges, since here the
aspect
ratios differ. By arranging the apertures to have different shapes in this
way, the
different types of aperture can be readily recognised by imaging equipment
(indeed the different shapes will generally be apparent to the human eye),
enabling the second data item to be decoded with a high degree of accuracy. In
addition, the number of different shapes which can be individually recognised
and distinguished from one another is virtually limitless, enabling a very
high
density of additional information to be encoded into the perforated security
element.
The "orientation" of an aperture refers to the layout of the aperture on the
surface of the security document, e.g. in terms of its rotational position
about an
axis normal to the surface of the security document through which the aperture
is made. Different orientations can also be achieved by reflecting the outline
of
aperture about an axis within the plane of the document. For example, a first
elongate rectangular aperture arranged parallel to an edge or other feature of
the document is considered to have a different orientation from a second
elongate rectangular aperture of the same aspect ratio having its long axis
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making a non-zero angle with the same feature of the document. By arranging
apertures making up the observable data item to have different orientations in
this way, a substantial volume of data can be encoded into the perforated
security element. Of course, in order that the different orientations are
recognisable, the apertures should not have a highly symmetric shape. In
particular, apertures having full circular symmetry will not be suitable for
this
purpose.
The encoded data item can be represented within the array of apertures
utilising
either different shapes o f the apertures, or different orientations (with all
apertures being of the same shape), or a combination of the two approaches,
using apertures of different shapes and/or orientations.
The observable data item, formed by the relative positions of the apertures in
the
array (independent of their shapes) can take any desirable form. For example,
the observable data item could be a perforated image, such as the outline of a
corporate logo, or any other pictorial design, e.g. a house, person or animal.
Preferably, at least the outline of such an image would be demarcated by the
arrangement of apertures, although additional apertures could be provided to
represent shading. However, in preferred examples, the observable data item is
a symbol, preferably a (single) letter or numerical digit. For instance, the
letter or
digit may be one of many making up a perforated code or serial number, as
described below. In all cases it is preferred that the observable data item
conveys some recognisable, intelligible information to the human viewer,
whether in the sense of alphanumerics or as a symbol or image.
The second data item can be converted into a corresponding arrangement of
aperture shapes and/or orientations in various ways. For example, the encoded
data item could be linked in a database to a randomly selected arrangement of
aperture shapes/orientations which should be applied to an observable data
item
in order to represent that encoded data item. Alternatively, a predefined
algorithm could be used to convert the encoded data item into shapes or
orientations. However, to make best use of the data storage capacity
available,
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preferably the encoded data item is represented by at least one of the
apertures
designated as a multi-level bit, the shape and/or orientation of the
designated
aperture representing its bit-level. The "bit-level" refers to the set of
available
"states" for each bit, e.g. "low" and "high", or "on" and "off'. By using at
least
5 some of the apertures to represent bits of data and using the shape or
orientation of the aperture to specify the level of each bit, a very large
number of
different encoded data items can be accommodated. The greater the number of
shapes and/or orientations (i.e. bit-levels) available, the greater the data
capacity
of the system. Preferably the value represented by the bit-level of the or
each bit
is related to the position of the bit within the array of apertures, although
this is
not essential. Thus, advantageously. the encoded data item is represented by
at
least one of the apertures designated as a multi-level bit, the shape and/or
orientation of the designated aperture in combination with the location of the
designated aperture within the array representing its bit-value.
Hence, in particularly preferred examples, the encoded data item comprises at
least one bit of data, the or each bit being represented by a selected
aperture
within the array, and each bit having a value selected from at least two bit-
values, represented by the shape, orientation and/or location of the or each
selected aperture. To increase the complexity of the security element, the
encoded data item preferably comprises a plurality of bits of data, each bit
being
represented by a separate selected aperture within the array.
As already noted, the observable data item formed by the arrangement of
apertures is preferably a single symbol such as a letter or numerical digit.
As
such, whilst the array could be a stand-alone feature, in many implementations
it
is preferred that the security element comprises multiple arrays of apertures,
each of the arrays of apertures forming a discrete observable data item and
each including an encoded data item represented by the occurrence of different
shapes or orientations of apertures within the array. For instance, each of
the
discrete observable data items may be a letter or digit, and encoded data can
be
provided within each of them. It should be noted however that further arrays
of
apertures without any encoded data could be included in the security element.
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Preferably, the discrete observable data items formed by the multiple arrays
of
apertures collectively form a visible code, the visible code being preferably
at
least part of a serial number or other unique identifier of the document of
value.
Advantageously, the encoded data items of the multiple arrays collectively
form
a hidden code. It should be noted that, unlike the observable data items, the
encoded data items in multiple arrays need not be discrete, i.e. recognisable
independently of one another. For example, depending on the algorithm used to
encode the data, it may be necessary to retrieve the arrangement of aperture
shapes or orientations from each of the multiple arrays of apertures before
the
data contained in any one can be decoded.
The encoded data item (or the hidden code, where there are multiple arrays of
encoded apertures) could contain any desirable information, and may also take
the form of a unique identifier. For instance, in the case of a passport or
identity
document, the encoded data item could relate to the identity of the document
holder, including for example, their name and/or date of birth. However, in
particularly preferred examples, the encoded data item (or hidden code) is
derived from the observable data item (or the visible code). This enables the
authenticity of the security element to be checked internally, i.e. against
itself.
This can be achieved in a number of ways. For example, the observable data
item could be linked in a database to a corresponding encoded data item.
However, preferably, the encoded data item is obtained by applying an
algorithm
to the observable data item. In particularly preferred embodiments the encoded
data item comprises verification data enabling verification of the observable
data
item. That is, the encoded data item acts as a check digit for confirming that
the
observable data item has been read correctly.
The apertures could be formed using any suitable process such as mechanical
perforation or grinding, but in preferred examples, the apertures are formed
by
laser perforation. This has the advantage that a large number of different
aperture shapes and orientations can be formed by the same apparatus.
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Any aperture shapes could be used as desired. However, in preferred
examples, the at least two different shapes comprise any of: circles,
ellipses,
triangles, squares, rectangles, polygons, stars, numbers, letters,
typographical
symbols or punctuation marks.
The size of the apertures may vary depending on their shape, but preferably
the
apertures forming the array each have approximately the same maximum
dimension or surface area. By arranging the different shapes of apertures to
be
of approximately the same size, the assortment of shapes is less immediately
apparent to an observer since the darkness (or brightness, if the document is
being viewed in transmission) will be approximately the same for each
aperture.
The apertures are preferably visible to the naked eye under reflected and
transmissive illumination.
As noted above, it is preferable that the encoded data item can be checked
against the observable data item itself. However, in other implementations,
the
encoded data item could be checked against other information provided on the
document of value. As such, the present invention further provides a security
element assembly, comprising a security element as described above and a
machine readable element, both the security element and the machine readable
element being arranged on a document of value, the machine readable element
having stored therein validation data against which the encoded data item can
be checked. Any suitable machine readable element could be used for this
purpose, but preferably the machine readable element comprises a RFID chip, a
barcode, a two-dimensional barcode, a digital watermark or an optical
character
recognition code such as a Machine Readable Zone (MRZ) on a passport. The
machine readable element can include the use of detectable materials that
react
to an external stimulus such as fluorescent, phosphorescent, infrared
absorbing,
thermochromic, photochromic, magnetic, electrochromic, conductive or
piezochromic materials.
The nature of the validation data will depend on the type of encoded data item
and the level of security required. For example, on a passport, the encoded
data
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item could relate to biographic or biometric data of the passport holder,
which
may already be stored in a RFID chip on the passport for other purposes, in
which case this stored data can also be used for validation. Alternatively, if
the
encoded data item is a code or similar, that code could be added to the
security
element for checking against the encoded data item. Thus, preferably the
validation data comprises the encoded data item. However, this is not
essential
and the validation data could, for example, comprise an algorithm through
which
the observable data item and the encoded data item are related, or parameters
of such an algorithm, to be inserted into an algorithm template known to the
document issuer.
The invention further provides a document of value comprising a security
element as described above or a security element assembly as described
above. Preferably the document of value is a passport, identification card,
licence, banknote, cheque or certificate.
The present invention further provides an authentication system for checking
the
authenticity of a document of value having a security element as described
above or a security element assembly as described above, the system
comprising an image capture device adapted to obtain an image of at least a
portion of the security element, an image processor adapted to identify the
shape of at least one selected aperture in the image and an authentication
processor adapted to determine whether the identified shape(s) and/or
orientations meet predetermined authentication criteria. The image capture
device can be implemented in any convenient manner, viewing the document of
value in transmitted or reflected light. A camera, scanner or any other
suitable
device for imaging the document of value could be used for this purpose. The
image processor preferably identifies the shapes (or orientations) and
locations
of the apertures within the array using shape-recognition software.
The authentication processor can be arranged to determine whether the
identified shapes or orientations in the image meet predetermined
authentication
criteria, i.e. whether the encoded data item is valid, in many different ways.
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As already mentioned, the encoded data item is preferably linked to the
observable data item. As such, in a preferred embodiment, the image processor
is further adapted to read the observable data item of the security element
from
the image, and the authentication processor is adapted to determine whether
the
identified shape(s) or orientation(s) meet predetermined authentication
criteria
based on the observable data item read from the security element. The
observable data item can be linked to the encoded data item (and hence the
shapes to be identified in the image) in various different ways. In one
preferred
example, the predetermined authentication criteria is associated with the
observable data item and the authentication processor is adapted to retrieve
the
predetermined authentication criteria associated with the observable data item
from a database by looking up the observable data item read from the security
element in the database. For example, here the authentication criteria may
comprise the arrangement of shapes or orientations expected to be found in a
security element having the retrieved observable data item. The expected
arrangement of shapes or orientations can then be compared with the identified
arrangement of shapes or orientations to determine whether there is a match.
If
so, authenticity of the document can be confirmed. In alternative preferred
implementations, the authentication processor is adapted to determine whether
the identified shape(s) or orientation(s) meet predetermined authentication
criteria by determining whether the relationship between the observable data
item read from the security element and the identified shape(s) or
orientation(s)
conforms to a predefined algorithm. The predefined algorithm may be stored by
the authentication processor and applied to all documents of value of the same
type. Alternatively the algorithm could be retrieved by looking up the
observable
data item read from the security element in a database.
Where the document of value is provided with a security element assembly
including a machine readable element in addition to the security element, the
authentication system preferably further comprises a device for reading the
machine readable element of the security element assembly and the
authentication processor is adapted to determine whether the identified
shape(s)
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or orientation(s) meet predetermined authentication criteria based on the
validation data stored in the machine readable element. The nature of the
reading device will depend on the type of machine readable element deployed.
For example, where the machine readable element is a RFID tag, the reading
5 device may comprise a corresponding RFID reader. Alternatively, if the
machine
readable device is optically readable, the reading device may comprise a
suitable imaging element and appropriate processing means. In this case, the
image capture device used to obtain an image of a portion of the security
element can also be used to image the machine readable element.
The present invention also provides a method of manufacturing a security
element on a document of value, comprising: obtaining a first data item and
generating an aperture array template, the apertures in the array template
being
arranged such that the first data item is observable from the arrangement of
apertures, obtaining a second data item and encoding the second data item
within the aperture array template by assigning one of at least two different
shapes or orientations to each of the apertures in the array template
according
to a predefined algorithm, whereby the encoded aperture array template
comprises apertures of at least two different shapes or orientations, the
occurrence of the different shapes or orientations representing the second
data
item, and perforating at least a portion of the security document according to
the
encoded aperture array template. As already described, by encoding a data
item within a perforated security element arranged to convey another data
item,
both the security and the information storage capacity of the security element
are greatly enhanced. The above method of manufacture is particularly
advantageous since this enables the element to be formed in a single
perforation
step.
Preferably the first (observable) data item is a symbol, preferably a letter
or
numerical digit.
In particularly preferred embodiments, the method further comprises
designating
at least one of the apertures in the aperture array template as a multi-level
bit
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and assigning the or each designated apertures a shape and/or orientation
representing a bit-level in accordance with the second data item.
Advantageously, the assigned shape and/or orientation of the or each
designated aperture in combination with its location within the array
represents a
bit-value in accordance with the second data item. As described above,
encoding the data in the form of bits makes best use of the available data
storage capacity. Preferably, the second data item comprises at least one bit
of
data, and the step of assigning one of at least two different shapes and/or
orientations to each of the apertures in the array template comprises
selecting
an aperture within the aperture array template to represent the or each bit of
data, and assigning a shape or orientation, based on the bit-value of the
respective bit of data, to the or each selected aperture.
As described above, the encoded or second data item can take many forms but
in preferred examples is associated with the observable (first) data item.
Hence,
advantageously, obtaining the second data item comprises performing an
algorithm on the first data item to generate the second data item.
The apertures can be formed in a number of ways but, preferably, the step of
perforation comprises laser perforation.
The invention further provides a method of manufacturing a security element
assembly on a document of value, comprising manufacturing a security element
as described above, providing a machine readable element on the document of
value, and storing, in the machine readable element, validation data against
which the encoded data item can be checked.
Examples of security elements, methods of making thereof and corresponding
authentication systems will now be described and contrasted with known
security elements with reference to the accompanying drawings, in which:
Figure 1 a schematically depicts a known example of a document of value;
Figure 1 b shows in detail a security element of the known document of value;
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Figure 1 c shows enlarged details of the security element of the known
document
of value, in cross-section;
Figure 2 shows a first embodiment of a security element, selected features
being
enlarged for clarity;
Figures 3a and 3b show schematic examples of security elements;
Figure 4 shows further schematic examples of security elements;
Figures 5a and 5b show a second embodiment of a security element, in the form
of a graphical simulation and as a perforation, respectively;
Figure 6 illustrates a process of encoding data into the security element;
Figure 7 illustrates an extract from a database associating encoded data items
with corresponding aperture shapes;
Figure 8 shows an example of a security element before and after encoding
according to an exemplary base-2 encoding system;
Figure 9 shows an extract from a database associating observable data items
with corresponding encoded data items;
Figure 10 schematically depicts a document of value according to a further
embodiment;
Figure 11 is an extract from a database associating data from a machine
readable element provided on the document with aperture shapes and/or
algorithm parameters;
Figure 12 schematically illustrates apparatus for manufacturing a security
element, and apparatus for authenticating a document provided with the
security
element;
Figure 13 depicts exemplary steps involved in the manufacture of a security
element;
Figure 14 depicts exemplary steps involved in the authentication of a document
carrying the security element;
Figure 15 shows a further embodiment of a security element; and
Figure 16 depicts four exemplary apertures in different orientations.
The ensuing description will largely focus on the example of security elements
applied to passports. However, it will be appreciated that the disclosed
security
elements can be applied to any document of value, including for example,
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identity cards, banknotes, certificates, cheques and the like. The document
typically comprises one or more sheets of material (such as paper, card,
polymer, a combination thereof or any other suitable material), through at
least
one of which the perforations will be made. The document could also take the
form of a label insert, tag or other element, which is for application to
another
article.
Figure 1 shows an example of a known passport booklet 1. The booklet 1
comprises front and rear covers 2a and 2b into which are bound a number of
internal pages 3. In this example, the booklet is shown to include four
internal
pages 3a, 3b, 3c and 3d but in practice any number of such pages could be
provided. The booklet 1 is provided with a number of security elements
including a perforated serial number, indicated generally in Figure 1a as item
4.
The perforated serial number 4 is shown in more detail in Figure 1 b, which is
an
image of the upper surface of any of the internal pages 3. The security
element
4 is a perforated serial number uniquely identifying the document, made up of
nine arrays of apertures (each designated 5), each representing a letter or
digit,
which together make up the code "A01234592". In this example, the serial
number is also provided with a check digit 6 which is generated according to a
function based on the depicted serial number and therefore acts to verify
whether the serial number has been read correctly. Each of the letters or
numbers 5 is made up of an array of apertures, of which two are labelled 5a
and
5b. The apertures are all of identical size and shape.
Figure 1c shows a cross-section through a portion of the security element 4
from
which it can be seen that each of the apertures 5a, 5b, etc, passes through
all of
the internal pages 3 of the document 1 (although this need not be the case).
In
this example, the apertures 5a and 5b are formed by laser perforation, which
results in the substantially conical shape visible in cross-section.
Figure 2 shows a first embodiment of a security element made in accordance
with the presently disclosed technique. The security element 15 comprises an
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array of apertures, ten in this example, positioned relative to one another on
the
page 3 so as to form the digit "0". The number and position of the apertures
is
selected in order to visibly convey the desired symbol "0" in accordance with
well
known techniques. However, the apertures are now formed from an assortment
of different shapes. In particular, whilst eight of the ten apertures are
circular,
those at positions 15c and 15h are star-shaped. Aperture 15c is a six-pointed
star, whilst that at 15h is a five-pointed star. Selecting the shape of each
aperture in the array can thus be used to convey an additional level of data
over
and above the visible data conveyed by the relative arrangement of the
apertures. This data is referred to as "encoded" since its meaning is not
directly
intelligible to the observer (unlike the digit "0" formed by the positions of
the
apertures).
Any assortment of shapes could be used to encode data into the aperture array
in this way. The above example uses a selection of circular and star-shaped
apertures, but in other examples, the apertures could be square, rectangular,
triangular, polygonal, elliptical, irregular or take the shape of well known
symbols
such as letters, numbers or punctuation marks. By forming the constituent
apertures in different shapes, the encoded data can be easily and reliably
recognised by suitable imaging apparatus provided with shape recognition
software. Since the number of different shapes which could be used to form the
aperture array is virtually unlimited, the amount of data which can be
represented by the different shapes is extremely high. As will be described
below with reference to Figure 15, as an alternative (or in addition to) the
use of
different shapes, the orientation of selected apertures within the array may
be
controlled to encode the data into the array.
Figure 3 illustrates the scenario where just two different shapes of aperture
are
made available for encoding purposes, here a circle and a square. Figure 3a
shows two security elements labelled (i) and (ii) alongside one another for
comparison. In each case, the security element comprises an array of apertures
16 of which only one is labelled (16j) for clarity. In security element (i),
all of the
apertures are circular, including 16j. However, in security element (ii),
aperture
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16j is square. Thus, aperture 16j can be said to represent one bit of data,
having
two bit-levels: either a low state (circular) or a high state (square). Figure
3b
illustrates ten security elements of similar construction, including examples
(i)
and (ii), in which different ones of the 14 apertures making up the letter "A"
are
5 selected to provide the bit of information. Since, in this example, the
letter "A" is
formed of 14 apertures, if every one of the apertures in the array is arranged
to
act as a bit of information with two bit-levels ("circle" or "square") the
encoded
data capacity of the single letter "A" would be 2 x 1014 bits. Of course, only
a
subset of the apertures in the array may be selected to act as data bits if
10 preferred. The data capacity of the security element can be increased still
further by increasing the number of different shapes of aperture available
(i.e.
increasing the number of bit-levels). This is illustrated schematically in
Figure 4
for ten further security elements, each of which again conveys the observable
data item "A". In this example, the security element 17, again comprising 14
15 apertures, is formed of an assortment of circular apertures, square
apertures,
four-pointed stars and five-pointed stars. For instance, in security element
17 of
Figure 4, the aperture in position 1 (labelled 17a) has a four-pointed star
shape,
the aperture in position 9 (labelled 17i) is a five-pointed star, and the
aperture in
position 13 (labelled 17m) is a square, whilst the remaining 11 apertures are
all
circular. If every aperture in the array is used to convey data and can take
one
of these four bit-levels (represented by the four different shapes), the
security
element 17 has an encoded data capacity of 4 x 1014 bits. The other security
elements illustrated alongside element 17 in Figure 4 provide examples of some
of the other permutations of apertures which may be used to form the same
observable data item "A" using these four selected aperture shapes. Each of
these configurations can correspond to a different encoded data item, the
nature
of which will be discussed further below.
Any of the security elements already described can be deployed as a stand-
alone security element, or used in conjunction with further arrays of
apertures in
order to increase the amount of data which is observable to a viewer. For
example, the security element 17 indicated in Figure 4 could be used to
replace
the first symbol "A" of the otherwise conventional perforated serial number 4
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16
depicted in Figure 1b. However, in order to increase the data capacity of the
security element still further, in many cases it is preferred that multiple
arrays of
apertures be provided, each one being encoded with data in accordance with the
above described principles. Figure 5 shows an example of this, depicting a
security element 25 according to a second embodiment. Figure 5a shows a
graphical representation of the security element 25, and Figure 5b shows the
same security element 25 perforated into a page 3 of a passport document such
as that shown in Figure 1a.
In this example, the security element 25 is made up of seven arrays of
apertures, each one forming an observable data item from the arrangement of
the apertures included therein. The first array 18 is arranged to form the
letter
"A", the second array 19 is arranged to form the number 1", the third array 20
is
arranged to form the number "2" and likewise arrays 21, 22, 23 and 24 are
arranged to form the digits "3", "4", "5" and "6" respectively. It will be
appreciated
that the data item observable from each array is a result of the position and
number of apertures in the array, and is independent of the individual
apertures'
shapes. Nonetheless, on close inspection it will be seen that each array of
apertures 18 to 24 is made up of an assortment of differently shaped apertures
in the same manner as discussed above in respect of Figure 4. Thus, an
encoded data item is included in each of the arrays 18 to 24, represented by
the
configuration of shapes. The encoded data items may be discrete (i.e.
recognisable from each individual array alone and separable from the other
encoded data), or may be inter-dependent on the data encoded within one or
more of the other arrays. For example, the first two arrays 18 and 19 could be
used individually to provide data capacity of 4 x 1014 and 4 x 1010 bits
respectively, or could be used combinedly to represent a single encoded data
item having a capacity of up to 4 x 1024.
However the data is encoded, the combined encoded data from the arrays 18
to24 as a whole represents a hidden code, the data capacity of which can be
increased by increasing the number of shapes available, increasing the number
of apertures in individual arrays and/or increasing the number of aperture
arrays
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17
included in the element. Alongside the encoded data, the security element 25
conveys a visible code (in this case "A123456") which is recognisable to a
human observer as well as to optical recognition software. Thus, the element
can be used to provide a serial number or indeed any other visible perforated
data, and can replace the conventional perforated serial number 4 shown in
Figure 1b. In general, each of the aperture arrays 18 to 24 will represent a
single, discrete data item such as a symbol, i.e. a letter, a numerical digit,
a
punctuation mark or the like. Alternatively, the array could be provided in
the
form of a perforated graphic such as the outline of a corporate logo or
similar. In
each case, the symbol is conveyed by the arrangement of the apertures, rather
than by their shapes.
As illustrated in all the above examples, it is generally preferred that the
different
shapes of aperture have approximately the same size. F or example, the
maximum dimension of each aperture or, even more preferably, the cross-
sectional area of each should be similar. This not only assists in rendering
the
observable data accurately (since the relative positions of the apertures are
not
distorted on account of the differing shapes ), but in addition, renders the
encoded data less conspicuous to an observer, since each of the apertures will
transmit or reflect approximately the same amount of light (depending on
whether the feature is being observed in reflected or transmitted light) and
hence
will not have a dramatically different appearance.
The apertures can be formed through the security document using any desirable
technique, such as perforation pins or grinding between suitably patterned
abrasive plates. However, in preferred implementations, the apertures are
formed by a laser controlled by a suitable processor as will be described
further
below. Laser perforation is preferable since not only does it permit each of
the
apertures to be formed using the same apparatus but it additionally imparts
characteristics such as blackening and a conical cross-section to the
perforations, which further increases the difficulty of forging a counterfeit.
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The data which is encoded into the security element through the use of
different
shapes can take many different forms, of which some examples will now be
provided. Figure 6 shows a generalised process for generating a security
element of the sort described above, to include encoded data. Here, an
exemplary observable data item 30 is the letter "A". In practice, the specific
observable data item may be obtained in a number of ways, for example from a
database or by reading data already provided on the document to which the
security element is to be applied. For example, where the observable data item
30 is to correspond to the serial number of a passport, this may already be
printed on at least one region of the passport and this could be read (by a
machine or otherwise) to determine the desired observable data item. The
observable data item may be a single letter, digit or other symbol or could be
a
longer code (such as the serial number A123456 shown in Figure 5), consisting
of multiple individual aperture arrays which can be encoded individually or
collectively (though not all of the arrays making up the code need to be
themselves encoded). The data 32 to be encoded into the observable data item
30 is also obtained and again this can be done in numerous ways as will be
described below. In this example, the encoded data item 32 is the numerical
sequence "08765", but in other implementations, text or graphical data could
be
used.
The observable data item 30 corresponds to an aperture array template in which
the positions of the apertures relative to one another are selected so as to
form
the desired data item, here the letter "A". In this example, the letter A is
formed
of 14 apertures although any suitable scheme could be used. A processor 40
then selects the shape of each aperture in the template according to
predefined
rules based on the data item 32 to be encoded. The result is an encoded
aperture template 35 which includes the same number and positional
relationship between the apertures as in the original aperture template, but
the
shape of at least some of the apertures has been selected to reflect the
encoded
data item.
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The encoding technique applied by processor 40 can take many different forms.
In a first example, where the number of possible encoded data items 32 is
finite,
the processor 40 could be linked to a database such as database 41 of which an
extract is illustrated in Figure 7. The database 41 associates each possible
encoded data item 32 with a corresponding sequence of shapes. For example,
here the data item "08765" is shown to correspond to the shape sequence
"circle, circle, circle, circle, square, star, circle, circle, circle,
circle", and it will be
seen that this corresponds to the first ten apertures of the encoded aperture
template 35 (counting from the top line of the letter "A", starting at the
left and
ending at the right-most circle of the letter's horizontal crossbar). A
sequence of
ten shapes has been selected in this example since each of the letters A to Z
and digits 0 to 9 is formed of a minimum of ten apertures using the present
aperture template scheme. However, any other number of shapes could be
used to encode the data as desired. If the aperture template for the
particular
observable data item includes more apertures than are used in the encoded
shape series, the remaining apertures in the template could be set to a
default
shape or could be allocated shapes at random in order to further increase the
difficulty of decoding the data for a potential counterfeiter. The database 41
linking the data items to the corresponding shape series would be made
available to authorisation systems used to validate the documents, in order to
decode the arrangement of apertures.
In an alternative embodiment, the processor 40 could be provided with a
predefined algorithm which is used to directly encode the data 32 into the
aperture template. An example of this using a base-2 system (where only two
aperture shapes are available) is depicted in Figure 8. Again, the observable
data item is the letter "A", and the aperture template comprises 14 spaced
apertures 30a to 30n, as depicted on the left hand side of Figure 8. The data
to
be encoded, here the number "08765", corresponds to the binary code
"10001000111101". Each of the aperture positions 30a to 30n is taken to
represent one of the binary positions, and the shape of each aperture is then
selected as high (square, "1") or low (circle, "0") as necessary. For example,
in
Figure 8, aperture 30a is taken to represent the highest binary positions, and
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aperture 30n the lowest. Therefore, the actual value represented by each bit
depends, in this example, on not only the shape of the aperture but also on
its
location within the array. For example, in a binary system, the lowest binary
position (here corresponding to aperture 30n) may represent units of 1, and
the
5 next-lowest binary position (aperture 301) units of 2, such that a "high"
bit level in
position 30n corresponds to a bit value of 1, but a "high" bit level in
position 301
corresponds to a bit value of 2. Other systems such as decimal could
alternatively be used. In other examples the bit-value could be disassociated
from the location of the shaped aperture (e.g. if the aperture chosen to carry
the
10 data is randomly selected, in which case the bit value indicated by the
displayed
bit-level could be determined solely from the shape/orientation, although a
large
number of available bit-levels may be necessary).
Similar systems can of course be employed with any number of shapes as
15 previously mentioned. Since the number of available bits will vary
according to
the original aperture template (and hence the nature of the observable data
item), it may be desirable to limit the number of bits utilised to the number
of
apertures available in the most sparsely populated aperture template of the
selected scheme. Alternatively, where a plurality of security elements are
20 provided, each being capable of holding encoded data, the encoded data item
could be encoded into a plurality of the arrays, either by making use the
increased number of apertures now available to attain the necessary data
capacity, or by splitting the encoded data item into two or more parts. For
example, in the present case, "087" could be encoded into a first array, and
"65"
into a second.
The nature of the encoded data itself can be varied. However, in order that
the
encoded data can be verified (and hence used to confirm the authenticity of
the
document) it is preferred that the encoded data item is linked in some way
with
data which is retrievable from the security document (unless the same encoded
data item is to be embedded into each document of the same sort). In preferred
examples, the observable data item provides this function. That is, the
encoded
data item is associated with the observable data item. In the case of a single
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21
aperture array such as that depicted in Figure 8, the encoded data item would
be
derived from the letter "A", which is the observable data item. Alternatively,
where multiple aperture arrays are provided in order to form a more complex
visible code, such as a serial number, all or a part of this code (whether
formed
of encoded aperture arrays or not) can be used as the basis for the encoded
data. For example, referring to the perforated serial number shown in Figure
5,
here the observable code is "A123456". The encoded data represented by the
assortment of shapes from which the perforated number is made is preferably
based on this serial number.
The association between the serial number and the encoded data can take a
number of forms. In one example, the serial number may be linked to a
corresponding encoded data item via a database such as 51 shown in Figure 9.
Here the encoded data items can be randomly allocated to each serial number
or could represent data otherwise linked to the serial number, such as the
passport holder's identity. When the authenticity of a document is to be
checked, the encoded data retrieved from the assortment of shapes in the
perforated feature can be compared with the serial number read visually from
the document and checked against one another by reference to the database
51. To further enhance security, the database 51 could additionally specify a
shape algorithm via which the encoded data item is to be input into the
aperture
template (in the process of Figure 6). For example, algorithm 1 could
correspond to a base-2 bit representation, algorithm to a base-3 bit
representation and algorithm 3 to a base-4 bit representation.
In other implementations, the use of a database can be avoided by linking the
serial number and encoded data by the use of a pre-programmed data
generation algorithm. One particular example of this will be provided below.
Depending on the parameters of the algorithm, the so-generated encoded data
can represent validation data against which the reading of the serial number
can
be checked. In other words, the encoded data acts as a check digit for the
serial
number and it is therefore possible to do away with any separate check digit
such as item 6 shown in Figure 1b. For example, the encoded data may
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represent a number which, together with the observable letters and numbers in
the serial number, satisfy a mathematical formula or equation. A common
equation used for this purpose in the art is the so-called "IBM check" which
is
used in the sequence of digits which makes up a credit card number. The
algorithm runs as follows: the digits in even positions, numbering from the
right,
are multiplied by two; any digits now greater than nine are reduced to a
single
digit by subtracting nine (equivalent to adding the two digits of the multi
digit
number) and finally all digits in the sequence are summed and a check digit
defined which makes the result evenly divisible by 10. This check digit can be
stored as the encoded data. Other possible check digit schemes also include
the modulo 11 scheme used in the International Standard Book Number (ISBN)
or the Electron Funds Transfer (EFT) routing number check which performs a
modulo 10 operation on a weighted sum of the digits in a sequence. Further
examples of check digits are described in patent application W02008/007064.
By linking the encoded data to the observable data item, the security element
is
internally checkable without reference to any other data source. However, in
addition or as an alternative, the encoded data item could be linked to other
information provided in the document. Figure 10 shows an exemplary document
of value 100, here an open passport booklet, having the security element 25
already described with reference to Figure 5. In addition, the passport 100
includes an RFID tag 90 and various printed information including a portrait
of
the holder 92 and a machine readable zone 93, which includes bibliographic
information relating to the holder. Information from the RFID tag 90 or the
printed information 92/93 could be used as the basis for the encoded data in
element 25. For example, each RFID tag 90 typically includes an ID number
which is not rewritable. This chip ID could be used as the encoded data hidden
in element 25 by virtue of the assortment of shapes. In this case, the data
items
need not be linked by a database, since the authentication system can be
equipped with a suitable reader for retrieving the information from the RFID
tag
90 which could then be compared with the encoded data from element 25.
Alternatively, to increase the security of the system, the readable chip ID
could
be used to look up other information from a database such as 61 shown in
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Figure 11 in order to arrive at the encoded data. For example, the database
could correlate chip IDs to corresponding shape sequences in much the same
way as already described with reference to Figure 7. Alternatively the chip
IDs
could be correlated to algorithms (as in Figure 9) or shape algorithm
parameters
as shown in Figure 11, both of which provide instructions as to how to arrive
at
the encoded data from a known starting point, such as the serial number or
other
observable data item taken from the element 25 itself. For example, where the
encoded data is a check digit based on the visible serial number, the database
61 could store parameters of the check digit equation.
Figure 12 schematically shows exemplary apparatus for manufacturing a
security element as described above and, additionally, apparatus for
authenticating a document of value to which such a security element has been
applied. The apparatus for manufacturing the security element is designated
generally as 70, whereas the authentication system is designated generally as
80.
In this example, the manufacturing apparatus comprises a laser 71 and a
controller 72 which is programmed to operate the laser 71 to perforate a
document 100 in accordance with the principles described above. Where the
encoded data is to be generated and encoded in accordance with a pre-defined
algorithm, this may simply be pre-programmed into the controller 72. However,
in other examples, the controller 72 may be linked to a database 73 for
retrieving
the appropriate encoding rules and/or encoded data item for the document 100.
If the encoded data is to be associated with other data stored on the document
(e.g. in a machine readable element), the manufacturing apparatus 70 may also
include a suitable reading device or retrieving data from the document, and/or
a
writing device for applying the data to the document in the desired format.
The authentication system 80 comprises an imaging device 81 such as a
camera or scan head which is used to image the document 100 at least in the
region of the perforated security element. An image processor 82 is
programmed with shape recognition software for recognising the various shapes
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of the apertures making up the security element. If the encoded data is linked
to
the observable data, the image processor 82 is preferably also configured to
recognise the observable data item from the relative positions of the
apertures.
Techniques for both of these processes are well known in the art. The
authentication system also includes a processor 83 for verifying whether the
encoded data is correct and hence whether the document 100 is genuine. The
manner in which this is performed will depend on the nature of the encoded
data
and any relationship between other data on the document 100. For example,
where the encoded data is linked to the observable data via a pre-determined
algorithm, the processor 83 may simply be programmed with the same algorithm
to enable the encoded data to be decrypted and compared with the visible code
read from the positions of the apertures. Where the relationship between the
encrypted data and the visible data is more complex, the processor 83 may be
in
communication with a database 85 which holds the necessary information. The
database 85 may be linked to the database 73 of the manufacturing system 70
(for example, via the Internet 75) to ensure that the information is regularly
updated.
Where the encrypted data is additionally or alternatively linked to other
information provided on the document of value 100, depending on the nature of
the machine readable element in which the information is stored, a further
reader
84 may be provided in the authentication apparatus to retrieve the relevant
data
from the document 100. For example, where the data is held in a RFID tag, the
reader 84 may comprise a RFID tag reader adapted to interrogate the RFID tag.
Other forms of reader may be provided as necessary.
A particular example of the manufacture of a security element in accordance
with the presently disclosed techniques and a corresponding authentication
method will now be described with reference to the flowcharts of Figures 13
and
14.
Figure 13 shows steps involved in manufacturing a security element. In this
example, the encoded data item is based on upon the perforated serial number
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(i.e. the observable data item) and is generated by applying a predefined
algorithm to the serial number. In step S100, the observable data item, such
as
the serial number to be applied to the document, is obtained. This may be
retrieved from a list of available numbers, an order specification, or from
the
5 document itself, for example. Here, the serial number is the code "A123456".
In
step S102, any letters included in the serial number are converted to their
ASCII
equivalents. Here, the letter "A" is converted into the number "65", so the
serial
number becomes "65123456". In step S104, the so-obtained serial number is
subtracted from a secret number, such as "9987534634". The secret number
10 could be particular to a certain document issuer or even particular to the
serial
number itself (in which case a database linking serial numbers to
corresponding
secret numbers would be required). The result is a new code, "9922411178".
Of course, in other examples, far more complex functions could be applied to
obtain such a code.
In step S106, the generated code is used as the encoded data item. A
corresponding series of shapes is obtained by applying a predefined algorithm
or
any other suitable method, such as those described with reference to Figures
6,
7 and 8. The aperture template corresponding to the original serial number can
then be updated with the desired aperture shapes and finally, in step S108,
the
document is perforated with apertures of the appropriate shapes. The resulting
security element visibly conveys the serial number "A123456" with the code
"9922411178" embedded within.
Figure 14 depicts steps involved in determining whether the same document is
authentic. In step S200, the perforated element is imaged to retrieve the
observable serial number and to recognise the shapes and positions of each
individual aperture. In step S202, the shape encoding algorithm applied in
step
S106 is reversed in order to convert the recognised arrangement of shapes into
the encoded data item. In the present example, this should result in the code
"9922411178".
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In step S204, the retrieved encoded data item is subtracted from the same
secret number as used in step S104, to give a result of "65123456".
Finally, in step S206, the result is compared with the retrieved serial
number,
converting any letters in the retrieved serial number to their ASCII
equivalent. If
the two are found to match, the authenticity of the document is verified.
As mentioned at the outset, instead of (or as well as) utilising different
aperture
shapes to encode data into the aperture array, the orientation of the
individual
apertures within the array may be controlled to carry the encoded data. The
method of encoding data into the array is the same as described above except
that, rather than select different aperture shapes, different orientations of
the
apertures relative to the document surface are chosen. All of the apertures
within the array could be configured to have the same shape, which may be
desirable to reduce the visual impact of the encoded data. Figure 15
illustrates a
further embodiment of a security element 130 formed in this way. Here, the
observable data item is an outline of a house, depicted using an array of star-
shaped apertures 130a, 130b, etc. The majority of the apertures forming the
array 130 are orientated such that the uppermost point of the star points in
the
direction parallel to a reference feature 135 of the document. For example,
the
apertures labelled 130a and 130b are orientated in this way. The feature 135
may be an edge of the document, or could be provided on the document in any
other desired way such as printing or as an aperture itself. Alternatively,
rather
than provide a separate orientation feature 135, the observable data item
itself
can be used to act as such a reference. For example, in the house outline of
Figure 15, the verticals forming the "door" of the house each define a
direction
(which in this example happens to be parallel to reference line 135), and the
orientation of each individual aperture 130 can be measured relative to this
direction.
To encode data into the element 130, the orientation of each of the apertures
(or
a selection thereof) forming the array is selected using a process analogous
to
that described above in respect of the previous embodiments. In this example,
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all of the apertures are arranged in the "upright" position with the exception
of
apertures 130x, 130y and 130z, each of which have been rotated by a small
angle, as will be seen from the Figure. This alternative orientation
represents a
second bit-level in the same way that a selection of an alternative shape was
used to represent data in the previous embodiments.
Clearly, the number of distinguishable orientations which can be achieved
using
any one aperture shape will depend on its geometry and, in particular, on its
level of symmetry. Due to the reasonably high level of symmetry of the five-
pointed star, it may be deemed that only the two alternative orientations
depicted
in Figure 15 are sufficiently distinguishable for use in encoding data.
However,
the data capacity can be increased by selecting a shape of lesser symmetry,
such as the letter "R" shown in Figure 16. This shows four examples of
apertures formed in the shape of the letter R, aperture 140a in the usual
"upright" orientation and apertures 140b, c and d showing the same shape
reflected about the vertical and horizontal axes. Of course, the letter could
also
be rotated about an axis normal to the surface of the document to produce an
even greater number of alternative orientations, which are readily
distinguishable
from one another.
The level of data storage can be even further enhanced by utilizing different
aperture orientations in combination with different aperture shapes in the
same
security element, with both the shapes and the orientations acting as
differentiators between bit-levels.
